The management of trash and refuse disposal has become increasingly important. Society presently creates a great volume of trash on a daily basis, in part due to the increased popularity of disposable products. In any event, it has become necessary to develop techniques and equipment that can process and dispose of greater and greater amounts of trash.
A principal mechanism for disposing of and processing significant volumes of trash is an industrial trash compactor. An industrial trash compactor comprises a compacting ram and a stationary receptacle (container) that, in combination one with the other, compresses trash to make efficient use of the container's total available volume. Typical receptacles include, for example, a dumpster that serves as a container for the trash. When the dumpster is full, it must be emptied. The typical dumpster often does not include a compactor. Thus, space is wasted if the trash is voluminous but capable of being downsized. As a result, the use of compactors has become commonplace. Such receptacles and compactors are often placed in high population areas such as apartments, condominiums, office buildings and the like. Users deposit their trash into the receptacle, whereupon the compactor system may compress the trash. The compactor is used periodically to compress the trash, thereby maximizing the amount of trash that can be contained in the receptacle.
Once the receptacle is full of compressed trash, it must be emptied. This involves exchanging the full receptacle with an empty receptacle by a specially-configured truck that empties the full receptacle at a suitable dumping site. It is very expensive to exchange, haul and dump the compacted trash. The exchanging, hauling and dumping processes are each expensive. Each process requires the maintenance and operation of specially-configured trucks. Such operations include not only the cost of operating the machinery, but also significant labor costs. Therefore, the exchange portion of the process is rendered even more expensive if the receptacle is not full because more exchanging, hauling and dumping is required to dispose of a given amount of trash.
However, the weight of the compacted trash can itself become a problem as many states have established weight limits for vehicles that travel the roadways. An overly full receptacle may exceed such a limit. Moreover, those skilled in the art will appreciate that a compactor and receptacle should not be overfilled such that trash is spilling onto the surrounding area. Use of a compactor that has been overfilled causes its own damage in environmental terms. In such an event, use of the, compactor is usually interrupted. Accordingly, to insure that the receptacle does not overflow, many users of receptacles and industrial compactors require the hauler to empty the receptacle frequently, even if the receptacle is not full. The hauler is paid by the trip, not in accordance with the fullness of the receptacle. This accepted method of waste disposal is therefore neither efficient nor cost effective. Ideally, the hauler would empty the receptacle only when the receptacle is full. Thus, there exists a tension in that the proper fullness of a compactor and receptacle assembly must be sufficient to warrant the cost of emptying the receptacle but not so "full" as to be overflowing the receptacle's capacity for containing compressed trash.
Others have addressed the problem of emptying trash receptacles at the optimum time and fullness. Such other methods have traditionally included the use of devices to sense and analyze fullness. One known prior art method is found in U.S. Pat. No. 3,765,147 to Ippolito, which discloses the placement of a photoelectric cell within the interior of the receptacle. The photoelectric cell senses when the receptacle is full. Use of a photocell can be inaccurate, however, because it can yield a premature indication that the receptacle is full. For example, if a large volume of highly compactable material such as foam rubber is in the receptacle, the photoelectric cell will register full despite the fact that additional material may be placed there, in. Further, should a long board or some other oddly-shaped object be put into the receptacle, it may trigger the photoelectric cell despite the fact that the receptacle may otherwise be empty. It is the nature of trash that it is neither uniform nor predictable in its composition. Thus, the potential for a false reading is an inherent limitation in the use of a photoelectric cell as a monitoring device.
U.S. Pat. No. 4,773,027 to Neumann et al. teaches another prior art method and provides an automated trash management system that monitors the fullness of various receptacles within a system. A plurality of remote status units are set up in operative association with a plurality of containers. The remote status units communicate with a central unit that monitors the fullness of each remote trash receptacle. When the central unit learns that a particular remote compacting unit is full as sensed by the remote status unit, a hauler is notified and dispatched to empty that remote compacting unit. The remote status unit of the Neumann et al. patent employs a sensing device that monitors pressure in the hydraulic system of the compactor. In other words, rather than utilizing a fixed position sensor as taught by Ippolito, Neumann et al. teaches sensing the amount of pressure in the hydraulic system that drives a piston to effect the trash compacting action to thereby determine whether the receptacle is full. As more trash is placed into the compactor, more pressure will be registered by the hydraulic system as it attempts to compress greater volumes of trash. In theory, if the receptacle is not full, something less than a predetermined maximum amount of pressure will be detected in the hydraulic system. Once filled to the desired level, a predetermined maximum amount of pressure is reached and sensed. At this time, the hauler is dispatched to empty the receptacle.
This prior art method of monitoring the fullness of a receptacle is also limited. Such a method depends entirely upon pressure within the hydraulic system to determine when the trash receptacle is full. If something other than a hydraulic compaction system is employed, the monitoring function is lost. Moreover, installation of such a system is necessarily time consuming and difficult. At least one hydraulic line must be removed and the sensor placed within the hydraulic system.
U.S. Pat. No. 5,016,197 to Neumann et al. (Neumann et al. '197) also determines fullness by monitoring hydraulic pressure. The Neumann '197 system constantly monitors the hydraulic pressure in the forward hydraulic lines by using a pressure extractor that finds the peak of a gradually increasing pressure function. The criteria used in the algorithm to determine the peak pressure must be individually assessed as the criteria are based upon the particular compactor/container unit on which the trash management system is applied. The peak of the gradually increasing pressure feature for the compaction cycle can be determined to be the back pressure on the compression member when it is at a position of maximum compaction. The maximum compaction readings are used as an indication of fullness of the trash receptacle. Since pressure sensors are placed in forward hydraulic lines, the irregularities introduced into the complete compaction cycle due to reverse motion do not have to be compensated for in the pressure algorithm.
Another embodiment of Neumann '197 suggests to monitor, as a substitute signal for instantaneous compression member pressure, a current signal proportional to the current applied to a motor within the hydraulic power pack. The substitute current signal is evaluated through the same peak pressure circuit as the pressure sensor signal discussed above. Monitoring a current signal proportional to a current within the hydraulic power pack via the same peak pressure analysis circuit produces erroneous results in various compactors.
Unlike pressure sensors which monitor pressure in forward hydraulic lines, current monitoring devices must be equipped to accurately differentiate between current due to reverse compaction ram motion and current due to forward compaction ram motion during a complete compaction cycle, as there is no separate current source for the forward and the reverse motions. In many compactors, because the hydraulic piston's face is unobstructed in the forward direction but obstructed by rods or other impedients in the reverse direction, the hydraulic efficiency of moving the compacting ram assembly forward is higher than the efficiency of moving the same assembly in the reverse direction. The lower efficiency in the reverse direction requires a higher current output in the reverse direction than in the forward direction for empty or partially full receptacles. If the current is monitored through the peak pressure circuit as suggested by Neumann et al, '197, erroneous or inaccurate data will result because the peak substitute current (pressure) recorded for the current profile of the cycle will be the reverse peak current and not the forward peak current. Further, because the current waveform is different from the pressure waveform, it is doubtful that current may be substituted for pressure to produce accurate data as suggested by Neumann et al, '197. The resulting inaccurate data will cause incorrect fullness determinations for various compactor cycles.
A typical trash compactor is an electromechanical device that utilizes an electric motor to power a hydraulic pump. The hydraulic pump, in turn, produces a hydraulic pressure that is applied to a piston in a compactor assembly that compresses the trash contained in the receptacle. The above-described prior art methods address the mechanical portion of the device used to effect compaction. The prior art has not adequately addressed the electrical energy that is also a part of the compaction process.
Thus, there is a need in the art for a low cost, accurate, simple, easily installed device that utilizes the electrical energy of the compaction process to determine the fullness of the receptacle. Such a device would preferably be adaptable to various types of composition assemblies and not adversely affected by weather conditions or other environmental hazards. Moreover, such a device would preferably be readily incorporated into a waste disposal system whereby the fullness of the receptacle could be remotely monitored and a hauler dispatched at an appropriate time.